This invention is directed to a method of manufacture of Surface Acoustic Wave (SAW) devices. Certain of these devices, such as reflective array compressors (RAC) or slanted array compressors (SAC), which perform pulse compression, chirp transformation and Fourier transformation are configured with input and output ports side-by-side at one end of the device and pointed down the long dimension of the device. Thus, surface acoustic waves are launched by the input transducer, reflected, and received by the output transducer. There is a strong tendency for a large component of an input signal to be fed laterally to the output transducer given the proximity of the input & output transducers. It was to prevent this feed-thru that earlier workers devised cutting a slot into the substrate between the ports, using diamond saws, and inserting a metal wall or septum into this slot. This slot could not be cut until the transducer structures were already in place. Therefore, mistakes at this stage were very costly. In fact, this operation frequently produced cracks in the substrate, thereby ruining the nearly completed device. It has not been possible to cut the slot first because the interdigital transducers (IDTs), which launch the SAWs, are applied by photolithographic methods. Cutting the slot first would cause edge effects in the photoresist applied, resulting in poor or unusable IDTs. These problems are completely obviated by our invention since the slot is no longer needed.